Customarily liquid containers are filled from without via the filling line, wherein a tapping cock or similar device is inserted at the admission location into the filling line and actuated to transmit the liquid.
Basically such a liquid container can also be a fuel tank or another operating liquid container of a motor vehicle; however, for the liquid containers currently under discussion, primarily it is urea solution containers that are considered, which are needed for a selective catalytic reaction in the exhaust system. The aqueous urea solution that is used for this as a rule is also designated in technical circles by its trade name of AdBlue®. The aqueous urea solution that is used to generate the selective catalytic reaction in the exhaust system must be refilled from time to time in the vehicle.
In filling the liquid container mentioned initially with liquid, as the degree of filling of the liquid container increases, pressure-related phenomena can occur in the interior of the container, which can cause the liquid already filled in the container to come sloshing out of it in an undesired spontaneous and sudden fashion.
For example, during the filling process in the tank of the liquid container, if gas, especially air, is included, and the filling process is continued, as the amount of liquid in the tank increases, the pressure in the liquid container can increase. This can get discharged spontaneously when liquid already filled into the liquid container is expelled.
To avoid such effects, liquid containers of the generic type in the prior art exhibit a check valve which closes when reaching a pre-set excess pressure, as it relates to the pressure at the admission location.
After the closing of the check valve, which customarily is provided in the filling line, the filling line is filled with liquid that passes through a tapping cock or a similar delivery mechanism, until the liquid column in the filling line reaches the tapping cock and the latter automatically switches off. Likewise the tapping cock can automatically switch off due to a pressure increase in the filling line, which pressure increase itself in turn can be caused by the filling of the filling line, closed by the check valve, with liquid.
At first, the liquid present in the filling line after closing of the check valve cannot pass into the tank, as long as the excess pressure in the tank cannot be reduced to the point where the check valve, also driven by the gravity of the liquid column found in the filling line, opens again.
To reduce the excess pressure in the tank, the prior-art liquid container customarily exhibits a special ventilation line, which, however, can also fill with liquid when the liquid container is filled with liquid. Then the ventilation line cannot carry out its ventilation function until it has been ventilated.
Therefore, the task of the present invention is to provide a further development of the liquid container named initially, so that it can be filled with liquid, with a simple structural design, while making it possible to reduce, or even avoid, the undesired spontaneous sloshing out of liquid already inserted.